Objective: To study the evolution of the antimicrobial resistance of non-typhi Salmonella in a Spanish Hospital during the last five years (20002005).

Materials and Methods: We studied 2309 Salmonella enterica ssp. enterica (designated ssp. I) isolated from clinical samples. All strains were isolated in the culture media routinely used for the isolation of enteric pathogens. Identification was made according to standard microbiological procedures and was confirmed by serotyping with commercial antisera (Difco Laboratories). Antimicrobial susceptibility was performed by the broth microdilution method using an automated system (Wider®). The antimicrobials studied were amoxicillin (Amx), amoxicillin-clavulanate (A/C), cotrimoxazole (Cotr) and ciprofloxacin (Cipr). The majority of the isolates (90%) belonged to serotypes 0:4 (B) and 0:9 (D1), and therefore only these have been included in this study.

Table 1. Evolution of number of isolates by serotype0:0D

2000

2001

2002

2003

2004

2005

0:4B

77

75

78

61

80

79

0:9D

236

311

323

274

295

151

Table 2. Evolution of resistance (%) to different antimicrobial agents by serotype

2000

2001

2002

2003

2004

2005

AMX

0:4B

80.52

68

85.9

75.41

71.25

51.9

0:9D

17.37

8.7

14

17.15

8.13

4

A/C

0:4B

1.3

0

2.56

3.3

0

0

0:9D

0.85

0

0.31

0

0.33

0

COTR

0:4B

23.37

13.33

19.23

27.9

10

12.65

0:9D

0.42

0.64

0.31

0.36

0.7

1.32

CIPRO

0:4B

0

0

0

0

1.25

1.26

0:9D

0

0

0

0

0

0

Results: See Tables 1 and 2.

Conclusions: 1) There is a strong relationship between serotype and antimicrobial resistance, being serotype 0:4(B) more resistant than 0:9 (D1). 2) In spite of the low resistance rate of serotype 0:4(B) to A/C there were high level (range 1731%) of moderately resistant (intermediate) strains. 3) Resistance to Cotr was low in serotype 0:9(D1) and moderate (range 13% to 23%) in serotype 0:4(B). 4) In 2004 and 2005 appeared two strains of serotype 0:4(B) resistant to Cipr, probably in relation with a high frequency of using these antibiotics as first choice drugs in the treatment of acute diarrhoea in adults.